iwlwifi: mvm: BT Coex - don't limit agg size in loose scheme

In loose BT Coex scheme, the aggregation size doesn't need to
be limited.

To avoid triggering it, remove a lockdep assertion - we need
to compute the AMPDU size limit from rate control code which
can't take mvm->mutex. This means that there is a race but in
the worst case, we will have a wrong AMPDU size limit which
is not a big issue.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>